Magnetic resonance imaging for diagnostic mapping of tissues

ABSTRACT

Methods of, and systems for, magnetic resonance imaging of diagnostic mapping of tissues, where sodium mapping is performed individually, as well as in combination with other images of tissue, such as T1ρ, T2, and/or T1-weighted images. In one method embodiment, a sodium image of the tissue is acquired during the same scanning session. Maps are constructed of each of the first and sodium images individually, and in combination, and further facilitate viewing in combination with each other as a single, blended image of the tissue. Maps of the images may be displayed individually or in combination with each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a continuation of InternationalApplication PCT/US2008/004780, filed Apr. 11, 2008 and published Oct.23, 2008, which claims benefit of U.S. Provisional Application Ser. No.60/923,215, filed Apr. 11, 2007, each of which is incorporated herein byreference.

STATEMENT OF GOVERNMENT INTEREST

This invention was made with government support by Grants R01AR045404and R01AR051041 awarded by The National Institutes of Health, andperformed at a NIH supported resource center (NIH RR02305). Thegovernment has certain rights in this invention.

FIELD OF THE INVENTION

The present invention relates to magnetic resonance imaging (MRI), andmore particularly, a magnetic resonance (MR) method and system fordiagnostic mapping of tissues.

BACKGROUND OF THE INVENTION

Osteoarthritis (OA) affects more than half of the population above theage of 65 (Felson, Epidemiol. Prev. 10:1-28 (1988); Felson, ArthritisRheum. 38:1500-1505 (1995)) and has a significant negative impact on thequality of life of elderly individuals (Guccione et al., Am. J. PublicHealth 84:351-358 (1994)). The economic costs in the US from OA havebeen estimated to be more than 1% of the gross domestic product. OA isnow increasingly viewed as a metabolically active joint disorder ofdiverse etiologies.

Articular cartilage is a connective tissue consisting of relatively fewcells and a highly charged and hydrated extracellular matrix (ECM). Theconstituents of the ECM are proteoglycans (PG), collagen, andnon-collagenous proteins and water (Grushko et al., Conn. Tiss. Res.19:149-176 (1989); Lohmander, J. Anatomy 184:477-492 (1994); Mankin etal., J. Bone Joint Surg-Am. 53:523-537 (1971)). Despite its remarkabledurability, degeneration of articular cartilage can result from eithernoninflammatory processes, such as osteoarthritis (OA), or inflammatoryprocesses, such as rheumatoid arthritis (RA). The biochemistry of earlystage OA is associated with loss of PG concentration, possible changesin the size of collagen fibril and aggregation of PG, increased watercontent, and increased rate of synthesis and degradation of matrixmacromolecules (Grushko et al., 1989; Lohmander, 1994). All of thesechanges in the macromolecular matrix lead to an alteration in themechanical properties of cartilage with the result that it can no longerserve as an effective load-bearing material.

As the disease progresses to its late stages, joint surface replacement(arthroplasty) is the only effective treatment. More recently, therehave been efforts in developing novel techniques for the treatment ofOA, such as chondro-protective drugs and re-population of the cartilagedefects by chondrocyte precursor cells with subsequent regeneration ofthe cartilage. Nevertheless, while current therapies have largely beendirected toward symptomatic relief of the disease, i.e., the developmentof drugs in animals that have shown the potential of protecting themacromolecules in cartilage from breakdown, they have proven to date tobe ineffective for halting the progression of OA. Moreover, a direct andaccurate, yet noninvasive, technique for validating the efficacy ofthese drugs in vivo, involving chondroprotective therapies, cartilagegrafting, gene therapy and tissue engineering over the long duration ofthe OA disease (10-20 years) in humans, and to assess their effect onmolecular changes associated with early stages of cartilage degenerationthat always precede structural changes.

Computed tomography (CT) and magnetic resonance imaging (MRI).Unfortunately, arthrography is an invasive technique that causes painand discomfort to the subjects, and is, therefore, not ideal for routineclinical use. CT cannot provide biochemical information, butconventional MRI can assess cartilage lesions and provide morphologicinformation about the cartilage damage. Thus, MRI has become themodality of choice for imaging joints due to its excellent definition ofligaments, cartilage, bone, muscle, fat and superior soft tissuecontrast (Smith, Magn. Reson. Imaging Clin. N. Am. 3:229-248 (1995);Sofka et al., Radiology 5:217-226 (2001)). For two decades, protonmagnetic resonance imaging (MRI) has shown its efficacy in thenoninvasive analysis of soft tissues, particularly in the diagnosis oftendinomuscular and osteoarticular diseases (Peterfy et al., Radiol.Clin. North Am. 34:195 (1996); Peterfy, Magn. Reson, Imaging Clin. N.Amer. 8:409-430 (2000)). Nevertheless, while conventional MRI can beused to quantify structural changes in articular cartilage, it cannotquantify early-stage molecular changes. Thus, the current lack ofadequate methods for quantifying these changes has hampered researchdirected towards the development of potential disease modifying agents.

Joint space narrowing determined from conventional radiographs is widelyaccepted as an indication for early diagnosis of OA. However, it doesnot yield accurate and quantifiable results on molecular changes thatprecede morphological changes.

Conventional proton MR techniques have been shown to provide informationabout late stages of degeneration in which structural defects arepresent (Recht et al., Am. J. Roent. 163:283-290 (1994); Peterfy et al.,Radiol. Clin. North Am. 32:291-311 (1994)). Recently, delayed gadolinium(Gd)-enhanced proton MRI of cartilage (dGEMRIC) (Bashi et al., Magn.Reson. Med. 36:665-673 (1996); Burstein et al., Magn. Reson. Med.45:36-41 (2001); Mlynarik et al., J. Magn. Reson. Imaging 10:497-502(1999)), positively charged nitroxide based techniques (Lattanzio etal., Trans. Orthop. Res. Soc. 25:1024 (2000)), and sodium MRI (Reddy etal., Magn. Reson. Med. 39:697-701 (1998); Shapiro et al., J. Magn.Reson. 142:24-31 (2000); Shapiro et al., Magn. Reson. Med. 47:284-291(2002)) have been employed to measure PG changes in cartilage both invivo and in vitro. However, these techniques have some practicallimitations. In dGEMRIC, long waiting period between contrast agentinjection and imaging and variation in intra tissue Gd-relaxivity maycontribute to the errors in PG quantization, thereby reducing theaccuracy of this technique in the detection of OA. Although sodium MRimaging has high specificity towards proteoglycans, it has an inherentlylow sensitivity and requires special radio-frequency hardwaremodifications before it can be used with a routine clinical imagingunit.

Spin lattice relaxation time in the rotating frame (T1ρ) has been shownto be sensitive to changes in PG content of cartilage (Duvvuri et al.,Magn. Reson. Med. 38:863-867 (1997); Akella et al., Magn. Reson. Med.46:419-423 (2001)). It is well suited for probing macromolecular slowmotions at high static fields without modifying MR system hardware(Sepponen et al., J. Computer Assisted Tomography 9:1007-1011 (1985);Santyr et al., Magn. Reson. Med. 12:25-37 (1989)) and provides analternative contrast compared to conventional MRI methods.

Since the first description by Redfield (Phys. Rev. 98:1787 (1955)),spin-locking techniques have been used extensively, to investigate thelow frequency interactions between the macromolecules and bulk water.Several authors have investigated the T1ρdispersion characteristics ofbiological tissues, including brain (Aronen et al., Magn. Reson. Imag.17:1001-1010 (1999); Rizi et al., J. Magn. Reson. Imaging 8:1090-1096(1998)), tumors (Aronen et al., Magn. Reson. Imag. 17:1001-1010 (1999);Markkola et al., Radiology 200:369-375 (1996)), and articular cartilage(Mlynarik et al., 1999; Akella et al., 2001; Duvvuri et al., 1997;Duvvuri et al., Radiology 220:822-826 (2001)). These studies havedemonstrated the potential value of T1ρ-weighting in evaluating variousphysiologic/pathologic states, but it is not without its drawbacks.

Nevertheless, the studies relating to the potential role of T1ρ-weightedMRI in measuring cartilage degeneration have all been restricted tosingle slice imaging, and hence, are impractical for the imaging of atypical anatomic volume. The use of single slice techniques results fromthe problem in making the spin-locking pulse slice selective, whereasmulti-slice imaging requires the application of multiple radio frequency(RF) pulse trains within a sequence repetition time (TR) to exciteseveral slices in a time efficient manner. Currently, T1ρ pulsesequences employ a non-selective RF pulse to spin-lock the magnetizationin the transverse plane following the application of a non-selective π/2pulse, exciting signals from the entire sample during each application,but the subsequent imaging sequence acquires data from only a singleslice, wasting the information from the remainder of the volume.Additionally, significant artifacts arise in T1ρ-weighted imaging whenmutation angles suffer small deviations from their expected values thatvary with spin-locking time and amplitude, severely limiting attempts toperform quantitative imaging or measurement of T1ρ relaxation times.

The current lack of adequate methods for quantifying these changes hashampered research directed towards the development of potential diseasemodifying agents.

SUMMARY OF THE INVENTION

To solve these and other problems, the present invention as describedherein, introduces a method of, and system for, magnetic resonanceimaging of diagnostic mapping of tissues, where sodium mapping isperformed individually, as well as in combination with other images oftissue, such as T1ρ, T2, and/or T1-weighted images.

In one method embodiment, a first image of a tissue is acquired during ascanning session. The first image includes a T1ρ, T2, and/or T1-weightedimage of the tissue. A sodium (e.g., Na) image of the tissue is acquiredduring the same scanning session. Maps are constructed of each of thefirst and Na images individually, and in combination with each other.This construction facilitates viewing the first and Na imagesindividually or in combination with each other as a single, blendedimage of the tissue.

The methods and systems of the invention may be adapted for use with awide array of clinical assessments, such as, but not limited to:intervertebral disk pathology, tumors, to study Alzheimer's disease,neuro-degeneration, myocardial abnormalities, arthritis, joint injuriesand abnormalities, heart disease, and scanning cartilage pathology. Anintegrated, and noninvasive measurement of molecular (PG, collagen andwater) and morphological (tissue volume) changes in cartilage by themethod and system herein, also enables the detection of OA, in its earlystages.

The imaging allows for more effective diagnosis of these conditions,through improved, comprehensive, and noninvasive imaging techniques.These measurements will help monitor disease progression, evaluatepotential strategies for disease management, and verify the efficacy ofdisease/disease modifying drugs.

In one embodiment, the use of the imaging modalities of T1ρ with sodiumimaging for diagnostic imaging of pathologies such as Alzheimer'sdisease, osteoarthritis, intervertebral-disc disease are techniques thatmay be used in combination or individually along with conventional MRIcontrast mechanisms (T1, T2) provides surprising and unexpected resultsthan when performed individually heretofore. Thus, the inventors havediscovered the relationship between sodium, T1ρ, and other contrastmechanisms, which provide the ability to more readily view images, anddetect and diagnose the diseases process earlier than can be done beforethis invention.

Reference herein to “one embodiment,” “an embodiment” or similarformulations herein, means that a particular feature, structure,operation, or characteristic described in connection with theembodiment, is included in at least one embodiment of the presentinvention. Thus, the appearances of such phrases or formulations hereinare not necessarily all referring to the same embodiment. Furthermore,various particular features, structures, operations, or characteristicsmay be combined in any suitable manner in one or more embodiments.

Additional objects, advantages and novel features of the invention willbe set forth in part in the description, examples and figures whichfollow, and in part will become apparent to those skilled in the art onexamination of the following, or may be learned by practice of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is explained with reference to the accompanyingfigures. In the Figures, the left-most digit(s) of the reference numberidentifies the figure in which the reference first appears.

FIG. 1 illustrates an MRI system within which the present invention canbe either fully or partially implemented.

FIG. 2 is an exemplary method for performing imaging acquisition throughthe use of an MRI system, such as the system of FIG. 1.

FIG. 3 shows a pseudo map of a T1ρ image of a tissue.

FIG. 4 shows a pseudo map of a Na image of a tissue.

FIG. 5 shows a pseudo-blended view of T1ρ images (that may or may notinclude T1 and/or T2 with images) blended with Na images.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION

Magnetic Resonance Imaging (MRI) is an imaging technique based in parton the absorption and emission of energy in the radio frequency range.To obtain the necessary magnetic resonance (MR) images, a patient (orother target) is placed in a magnetic resonance scanner. The scannerprovides a magnetic field that causes target atoms to align with themagnetic field. The scanner also includes coils that apply a transversemagnetic field. Radio-frequency (RF) pulses are emitted by the coils,causing the target atoms to absorb energy. In response to the RF pulses,photons are emitted by the target atoms and detected as signals inreceiver coils.

Present diagnostic strategies, such as CT, and T1- and T2-weightedmagnetic resonance imaging, are only sensitive in advanced stages of thedisease. Described herein is an innovative MR package that providescomplete information about the biochemical and morphological state ofthe tissue. The MR package includes a process of pre-imaging,image-acquisition, post-processing, and image-viewing steps designed forphysicians to diagnose tissues at earlier stages of disease.

FIG. 1 illustrates an MRI system 100 within which the present inventioncan be either fully or partially implemented. As appreciated by thoseskilled in the art, there are various ways to implement an MRI system100. In one possible embodiment, MRI system 100 includes hardwarecomponents 102, and a control system 104. As is well known by thoseskilled in the art, typical hardware components 102 include: a magnet106 for producing a stable and very intense magnetic field, and mayinclude one or more coils, such as gradient coil for creating a variablefield, and radio frequency (RF) coil, for transmitting energy andencoding spatial positioning.

Control system 104 controls hardware components 102, such as thescanning sequencing operations, and processes information obtained fromscanning. Control system 104 may be implemented as a computer or controldevice, which includes at least one processor 112, and memory 114.Memory 114 may include volatile memory (e.g., RAM) and/or non-volatilememory (e.g., ROM). It is also possible for other memory mediums (notshown) having various physical properties to be included as part ofcontrol system 104. The images and maps provided using such systems arereferred to as “computer-generated.”

Control system 104 may also include code 116 stored in memory 114, suchas software and/or firmware that causes MRI system 100 to performscanning, and processing of images.

Much of the discussion below will focus on embodiments for performingoperations of control system 104—that may be embodied as code 116 ormedia—used to control MRI system 100. In particular, image acquisition,post processing, and image viewing stages. As appreciated by thoseskilled in the art, any suitable pre-imaging techniques may be usedprior to acquiring images.

As used herein, the term “acquiring,” “acquire,” or variations thereof,refers to the act of (i) receiving data signals indicative of imagesreceived from hardware 102 and stored as data in memory 114, or (ii)sending instructions to hardware 102 from control system 104 to obtainthe images, and then obtaining/storing the images, or (iii) reading datafrom memory 114 corresponding to images previously received fromhardware 102, and stored in memory, (iv) or any combination of thereof.

FIG. 2 is an exemplary method 200 for performing imaging acquisitionthrough the use of an MRI system, such as system 100 of FIG. 1. Method200 includes blocks 202, 204, 206, 208, 210, and 212 (each of the blocksrepresents one or more operational acts). The order in which the methodis described is not to be construed as a limitation, and any number ofthe described method blocks may be combined in any order to implementthe method. Furthermore, the method can be implemented in any suitablehardware, software, firmware, or combination thereof. Additionally,although each module in FIG. 2 is shown as a single block, it isunderstood that when actually implemented in the form ofcomputer-executable instructions, media, logic, firmware, and/orhardware, that the functionality described with reference to it, may notexist as separate identifiable block.

In block 202 of FIG. 2, a first image of a tissue during a scanningsession is acquired. The first image may include T1ρ, T1-weighted,and/or T2 images of a localized tissue (in general, collectivelyreferred to as a T-image for claim purposes). The acquisition of thefirst image may involve several subcategories of operations.

For example, in one embodiment, MRI system 100 (FIG. 1) may acquire athree-plane image of localized tissue. It is presumed that pre-imagingtechniques are performed prior to, or concurrent with, acquisition of athree-plane image.

If the tissue has previously been imaged, MRI system slice planning canbe coordinated by real-time coregistration of old and new localizers.

Another subcategory step of block 202 may include acquiring athree-dimensional T1-weighted isotropic resolution scan with fullcoverage of the tissue. Alternatively, in other embodiments, T2 imagescans with full cover the tissue may be acquired.

In one embodiment, as another potential subcategory operation of block202, multiple T1ρ-weighted images with incremental spin lock durationand/or amplitude are also acquired, covering the same volume asT1-weighted images.

In block 204, an Na image of the tissue is acquired during the samescanning session as the acquisition of the first image in block 202.This operational block may also involve several subcategoriesoperations.

For example, in one embodiment, if a spectrometer (not shown) of MRIsystem 100 (FIG. 1) has multiple RF channels capable of broadband ordual-band RF transmission and signal reception, then concurrent withboth T1- and T1ρ-weighted image acquisition in block 202, an ultrashortTE or radial magic echo of ²³Na images may be acquired. As appreciatedby those skilled in the art having the benefit of this disclosure, inalternative embodiments, other quantities of Na images may be acquired.

Alternatively, in another embodiment, if the spectrometer of MRI system100 (FIG. 1), does not have multiple RF channels, but is capable ofbroadband RF transmission and signal reception, then ultra short TEradial or radial magic echo ²³Na images are acquired during the ¹Hmagnetization regrowth period between balanced Steady-State FreePrecession (bSSFP) readout and the next spin-lock duration. This time isequivalent to TR-SL-bSSFP-PREP, where SL denotes the spin lock duration,bSSFP denotes the readout duration and PREP denotes the duration of anyadditional preparation periods, i.e. dummy pulses (linear, constant orotherwise), fat saturation periods or inversion recovery periods. TR isthe delay between subsequent acquisitions.

In one embodiment, pre-preparation involves several optional RF andgradient pulses that may be activated at any time during a sequence tomodify T1ρ contrast. It is appreciated by those skilled in the art afterhaving the benefit of this disclosure that preparation periods may beused to complement T1ρ imaging in order to reduce blurring, artifacts,etc. These are not necessarily mutually exclusive from the imageacquisition period. Examples of pre-preparation pulses include, but arenot limited to, Inversion, Gradient Tagging, Diffusion-Weighting, andSpectral Excitation/Saturation.

In one embodiment, any of the foregoing operations may be repeated usinga coronal view. As appreciated by those skilled in the art, having thebenefit of this disclosure may be included as part of process 200.Alternatively, obtaining images from the perspective of the coronal viewmay not be performed.

While FIG. 2 shows a specific example of image acquisition process, itshould be understood by those skilled in the art, after having thebenefit of this disclosure that acquisition of a first image (such asT1ρ, T2, and/or T1-weighted image) may be performed in combination withthe acquisition of the Na image. The exact techniques used to acquirethese images may vary. Thus, many modifications to the sequence ofoperations shown in FIG. 2 may achieve the same result of imageacquisition. Some examples of generalizations of the pulse sequenceinclude interleaved sodium and proton MRI, or alternately proton andsodium images.

In block 206, a map of the first image (first T-image) is constructed.For example, T1ρ images are constructed from multiple T1ρ-weighted andstored in memory 114 (FIG. 1). Such maps are computer-generated from theacquired images entered into the computer. FIG. 3 shows a map 300 of aT1ρ image of a tissue.

Referring back to FIG. 2, T1-weighted images are constructed. T2 imagesmay also be constructed. Maps may also be semi-automatically segmentedfor viewing, presentation or display. T1ρ-weighted images or T2 images,are combined using any suitable volumetric or multiple slice imagingsequence on a computer, as would be appreciated by those skilled in theart.

In block 208, a map of the Na image is constructed and stored in memory114 (FIG. 1). Sodium concentration (FCD) maps are constructed fromnormalized phantoms contained within the imaging region of interest orfield of view (FOV). FIG. 4 show a pseudo map 400 of a Na image of atissue.

Referring back to FIG. 2, in block 210, a blended mapping of the firstand Na images is constructed and stored in memory 114 (FIG. 1). Forexample, in one embodiment, T1ρ images are co-registered withT1-weighted, and sodium images to correct for motion that occurredduring the scan if any did occur. If there were no motion, there wouldbe no motion correction, but they may still be blended together.T1-weighted images (volume data) are combined with the T1ρ relaxationtimes (ti) and Na concentration to provide at least two metrics fortissue assessment.

In block 212, a blended view of maps 300 and 400 are viewable and/ordisplayed, as a blended view 500 (FIG. 5) of the tissue. That is,multi-parameter image maps (such as shown in FIGS. 3 and 4) are uploadedto an image viewing database displayed. A user may then select todisplay a blended view 500 of the T1 and or T2 with T1ρ and or Naimages, such as shown in FIG. 5. Or alternatively, the user may selectto view the maps individually, per block 214 of FIG. 2. That is, theuser may select to display a single modality image and query theparameter values of the other two images by cursor inspection, orregion-of-interest (ROI) analysis.

As a result of using method 200, a comprehensive tissue-mapping packagemay now be made available to physicians for diagnosing osteoarthritis,breast cancer, intervertebral-disk pathology, tumors, Alzheimer'sdisease, and neuro degeneration, among others. With respect toosteoarthritis, method 200 allows for T1ρ relaxation mapping, sodiummapping, and T2 mapping of the joints for OA diagnosis, particularly inthe early stages.

In alternative embodiments, a magnetic-resonance-imaging system isprovided, the system having pulses delivered by RF scanner coil(s),wherein the system comprises: a device in the system for acquiring ontoa computer, a T1ρ image of a tissue during a scanning session; a devicein the system for acquiring onto the computer, an Na image of the tissueduring the same scanning session; a computer means for constructingcomputer-generated maps of each of the T1ρ image and the Na imagesindividually, and simultaneously in combination with each other, suchthat the T1ρ and Na images are viewable in at least one of individuallyand in combination with each other as a single, blended image of thetissue; and a device for displaying same. Also provided is an MRI systemfurther comprising: a device for acquiring a T1-weighted image duringthe same scanning session, and constructing a computer-generated map ofthe T1-weighted image in combination with the T1ρ and Na images, suchthat the T1-weighted, T1ρ, and Na images are viewable as a single,blended image of the tissue; and a device for displaying theT1-weighted, T1ρ, and Na images as a single, blended image of thetissue. In addition, an MRI system is provided, further comprising: adevice for acquiring a T2 image during the same scanning session, andconstructing a map of the T2 image in combination with the T1ρ,T1-weighted, and Na images, such that the T2, T1ρ, T1-weighted and Naimages are viewable as a single, blended image of the tissue; and adevice for displaying the T2, T1ρ, T1-weighted and Na images as asingle, blended image of the tissue.

Each and every patent, patent application and publication that is citedin the foregoing specification is herein incorporated by reference inits entirety.

While the foregoing specification has been described with regard tocertain preferred embodiments, and many details have been set forth forthe purpose of illustration, it will be apparent to those skilled in theart that the invention may be subject to various modifications andadditional embodiments, and that certain of the details described hereincan be varied considerably without departing from the spirit and scopeof the invention. The embodiments described herein are to be consideredin all respects only as exemplary and not restrictive. The scope of theinvention is, therefore, indicated by the subjoined claims rather by theforegoing description. All changes which come within the meaning andrange of equivalency of the claims are to be embraced within theirscope.

What is claimed is:
 1. A method for magnetic resonance imaging (MRI) fordiagnostic mapping of tissue, the MRI system having pulses delivered byRF scanner coil(s), the method comprising: acquiring a first T-image ofthe tissue during a scanning session, wherein the first image includesat least one of a T1ρ, a T1-weighted, and a T2 image; acquiring a Naimage of the tissue during the same scanning session; and constructingcomputer-generated maps of each of the first T-image and Na imageindividually, and in combination with each other, such that the firstand Na images are viewable in at least one of individually and incombination with each other as a single, blended image of the tissue. 2.The method of claim 1, further comprising simultaneously displaying thefirst T-image and the Na image in combination with each other, as asingle, blended image of the imaged tissue.
 3. The method of claim 2,further comprising studying cartilage pathology and arthritis utilizingthe simultaneously displayed first T-image and Na image in combinationwith each other.
 4. The method of claim 2, further comprising studyingany of the following: intervertebral disk pathology, tumors, Alzheimer'sdisease, or neurodegeneration, utilizing the simultaneously displayedfirst T-image and Na image in combination with each other.
 5. The methodof claim 1, wherein the first T-image and the Na image are three-planeimages of the tissue.
 6. The method of claim 1, wherein the firstT-image is a T1ρ image.
 7. The method of claim 6, further comprisingstudying any of the following: cartilage pathology and arthritis,intervertebral disk pathology, tumors, Alzheimer's disease, orneurodegeneration utilizing the simultaneously displayed first T-imageand Na image in combination with each other.
 8. One or morecomputer-readable media for magnetic resonance imaging for diagnosticmapping of tissue, the medium having computer-executable instructions,which when executed by one or more processors of the MRI system havingpulses delivered by RF scanner coil(s), cause the device to perform thesteps of claim
 1. 9. A method for magnetic resonance imaging (MRI) fordiagnostic mapping of tissue, the MRI system having pulses delivered byRF scanner coil(s), the method comprising: acquiring a T1ρ image of thetissue during a scanning session; acquiring a Na image of the tissueduring the same scanning session; constructing a computer-generated mapof each of the T1ρ image and the Na image individually, such that theT1ρ image and the Na images are viewable individually; constructing acomputer-generated map of each of the T1ρ image and the Na image insimultaneous combination, such that the T1ρ and Na images are viewableas a single, blended image of the tissue; and displaying the single,blended image of the tissue.
 10. The method of claim 9, furthercomprising using the single, blended image of the tissue to studycartilage pathology and arthritis.
 11. The method of claim 9, furthercomprising using the single, blended image of the tissue to study atleast one of: intervertebral disk pathology, tumors, Alzheimer'sdisease, and neuro degeneration.
 12. The method of claim 9, furtheringcomprising: acquiring a T1-weighted image during the same scanningsession, and constructing a computer-generated map of the T1-weightedimage in combination with the T1ρ and Na images, such that theT1-weighted, T1ρ, and Na images are viewable as a single, blended imageof the tissue; and displaying the T1-weighted, T1ρ, and Na images as asingle, blended image of the tissue.
 13. The method of claim 12, furthercomprising using the single, blended image of the tissue to studycartilage pathology and arthritis.
 14. The method of claim 12, furthercomprising using the single, blended image of the tissue to study atleast one of: intervertebral disk pathology, tumors, Alzheimer'sdisease, and neuro degeneration.
 15. The method of claim 12, furthercomprising: acquiring a T2 image during the same scanning session, andconstructing a map of the T2 image in combination with the T1ρ and Naimages, such that the T2, T1ρ, and Na images are viewable as a single,blended image of the tissue; and displaying the T2, T1-weighted, T1ρ,and Na images as a single, blended image of the tissue.
 16. The methodof claim 15, further comprising using the single, blended image of thetissue to study cartilage pathology and arthritis.
 17. The method ofclaim 15, further comprising using the single, blended image of thetissue to study at least one of: intervertebral disk pathology, tumors,Alzheimer's disease, and neuro degeneration.
 18. Amagnetic-resonance-imaging system, having pulses delivered by RF scannercoil(s), the system comprising: device in the system for acquiring ontoa computer, a T1ρ image of a tissue during a scanning session; device inthe system for acquiring onto the computer, an Na image of the tissueduring the same scanning session; computer means for constructingcomputer-generated maps of each of the T1ρimage and the Na imagesindividually, and simultaneously in combination with each other, suchthat the T1ρ and Na images are viewable in at least one of individuallyand in combination with each other as a single, blended image of thetissue; and device for displaying same.
 19. The system of claim 18,furthering comprising: device for acquiring a T1-weighted image duringthe same scanning session, and constructing a computer-generated map ofthe T1-weighted image in combination with the T1ρ and Na images, suchthat the T1-weighted, T1ρ, and Na images are viewable as a single,blended image of the tissue; and device for displaying the T1-weighted,T1ρ, and Na images as a single, blended image of the tissue.
 20. Thesystem of claim 19, further comprising: device for acquiring a T2 imageduring the same scanning session, and constructing a map of the T2 imagein combination with the T1ρ, T1-weighted, and Na images, such that theT2, T1ρ, T1-weighted and Na images are viewable as a single, blendedimage of the tissue; and device for displaying the T2, T1ρ, T1-weightedand Na images as a single, blended image of the tissue.